Hybrid powertrain system

ABSTRACT

A powertrain system is provided that includes a first prime mover and change-gear transmission having a first input shaft and a second input shaft. A twin clutch is disposed between the first prime mover and the transmission. The twin clutch includes a first main clutch positioned between the first prime mover and the first input shaft and a second main clutch positioned between the first prime mover and the second input shaft. The powertrain system also includes a second prime mover operably connected to one of the first and second input shafts.

This Invention was made with Government support under NREL SubcontractNo. ZCL-2-32060-01, Prime Contract DE-AC36-99G010337 awarded by theDepartment of Energy. The government has certain rights in thisInvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a vehicle powertrain systemand, more particularly, to a hybrid powertrain system employing at leasttwo prime movers and a twin clutch transmission.

2. Description of the Related Art

Various types of twin clutch transmissions have been proposed and putinto practical use, particularly in the field of wheeled motor vehicles.Traditional twin clutch transmissions are of a type in which gears areparted into two groups, each group having an individual main clutch, sothat the operative condition of each group of gears is carried out byselectively engaging a corresponding main clutch. Twin clutchtransmissions are used in vehicles to improve the transition from onegear ratio to another and, in doing so, improve the efficiency of thetransmission.

Hybrid vehicle powertrain systems employing two or more prime movers arealso known in the art. A typical hybrid powertrain system includes aninternal combustion engine that is strategically operated in combinationwith an electric motor to provide driving torque to the wheels of avehicle. Among other features, hybrid powertrain systems improve vehiclefuel economy by allowing a reduction in the displacement of the internalcombustion engine and by recapturing and using kinetic energy lostduring vehicle braking in a conventional powertrain system.

SUMMARY OF THE INVENTION

The present invention is an improved vehicle powertrain system thatutilizes one or more features of a twin clutch transmission and a dualprime mover hybrid powertrain arrangement. In an embodiment of theinvention, a powertrain system is provided that includes a first primemover and change-gear transmission having a first input shaft and asecond input shaft. A twin clutch is disposed between the first primemover and the transmission. The twin clutch includes a first main clutchpositioned between the first prime mover and the first input shaft and asecond main clutch positioned between the first prime mover and thesecond input shaft. The powertrain system also includes a second primemover operably connected to one of the first and second input shafts. Atransmission and twin clutch arrangement for a dual prime moverpowertrain system is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic representation of a powertrain system accordingto an embodiment of the present invention; and

FIG. 2 is a schematic illustration of a transmission and twin clutcharrangement according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a hybrid powertrain system 20 is shown inaccordance with an embodiment of the present invention. In theillustrated embodiment, powertrain system 20 includes a first primemover 22, such as a spark-ignited or compression-ignited internalcombustion engine, a transmission 24 and a second prime mover 26, suchas an electric motor/generator or hydraulic motor/pump. A main clutchassembly 28 is positioned between first prime mover 22 and transmission24 to selectively engage/disengage first prime mover 22 fromtransmission 24.

In an embodiment, powertrain system 20 also includes an electroniccontrol unit (ECU) 30 for controlling operation of first prime mover 22,main clutch assembly 28, second prime mover 26 and transmission 24. Inan implementation of the invention, ECU 30 includes a programmabledigital computer that is configured to receive various input signals,including without limitation, the operating speeds of first and secondprime movers 22 and 26, transmission input speed, selected transmissionratio, transmission output speed and vehicle speed, and processes thesesignals accordingly to logic rules to control operation of powertrainsystem 20. For example, ECU 30 may be programmed to deliver fuel tofirst prime mover 22 when first prime mover 22 functions as an internalcombustion engine. To support this control, each of first prime mover22, second prime mover 26 and main clutch assembly 28 may include itsown control system 29 contained within ECU 30. However, it will beappreciated that the present invention is not limited to any particulartype or configuration of ECU 30, or to any specific control logic forgoverning operation of powertrain system 20.

In an embodiment of the invention, powertrain system 20 also includes atleast one energy storage device 31 for providing energy to operate firstand second prime movers 22, 26. For example, energy storage device 31may contain a hydrocarbon fuel when first prime mover functions as aninternal combustion engine. In another example, energy storage device 31may include a battery, a bank of batteries or a capacitor when secondprime mover 26 functions as an electric motor/generator. Alternatively,energy storage device 31 may function as a hydraulic accumulator whensecond prime mover 26 functions as a hydraulic motor/pump. While ECU 30provides first and second prime movers 22, 26 in communication withenergy storage device(s) 31 when operation of first and second primemovers 22, 26 is desired, the energy is not necessarily routed throughECU 30 as shown in FIG. 1.

Referring to FIG. 2, an embodiment of a transmission and clutcharrangement for use in a dual prime mover powertrain system is shown. Inthe illustrated embodiment, transmission 24 includes a first input shaft40, a hollow second input shaft 42, which is coaxially disposed aboutthe first input shaft 40 to achieve a relative rotation therebetween, acountershaft 44 that extends substantially parallel with first andsecond input shafts 40 and 42, and a plurality of gears which arearranged on and/or around shafts 40, 42 and 44. Although shafts 40, 42and 44 are illustrated as being mounted in a common plane in FIG. 2,these shafts may be arranged in different planes.

When second prime mover 26 functions as a motor/generator, asillustrated in FIG. 2, second input shaft 42 is operably connected forrotation with a rotor 43 that is positioned within a stator 45, as isknown in the art. In a particular implementation, rotor 43 is splined tosecond input shaft 42 for rotation therewith; however, otherconfigurations known in the art may also be used to connect second inputshaft 42 for rotation with rotor 43. As noted above, operation of secondprime mover 26 is not limited to that of an electric motor/generator.For example, second prime mover 26 may function as a hydraulicmotor/pump.

In the embodiment shown in FIG. 2, first input shaft 40 is connectableto an output portion 46 of first prime mover 22, such as a flywheel,through a first main clutch C1 that is used to establish even speedgearing (viz., second speed gearing, fourth speed gearing and reversegearing), while second input shaft 42 is connectable to flywheel 46through a second main clutch C2 that is used for establishing odd speedgearing (viz., first speed gearing, third speed gearing and fifth speedgearing). In an embodiment of the invention, first and second mainclutches C1 and C2 are of a normally ON type, which assumes the ON(viz., engaged) state due to a biasing force of a spring and the likeunder a normal condition and establishes the OFF (viz., disengaged)state due to work of a hydraulic or electric actuator upon receiving agiven instruction. Engagement and disengagement of first and second mainclutches C1, C2 may function automatically under the control of ECU 30,and without intervention of a vehicle driver, when powertrain systemsoperates like an “automatic” transmission.

To first input shaft 40 there are connected a 2nd speed input gear 48, a4th speed input gear 50 and a reverse input gear 52, such that gears 48,50 and 52 rotate together with first input shaft 40. Similarly, tosecond input shaft 42 there are connected a 5th speed input gear 54, a3rd speed input gear 56 and a 1st speed input gear 58, such that gears54, 56 and 58 rotate together with second input shaft 42. The number ofinput gears provided on first and second input shafts is not limited tothe number shown in FIG. 2, and may include more or less input gearsdepending on the number of ratios desired in the transmission. The term“gear,” as stated herein, is used to define the toothed wheelsillustrated in FIG. 2, as well as manufacturing the toothed features ofthe wheels directly into first and second input shafts 40, 42 andcountershaft 44.

To countershaft 44 there are rotatably connected a 1st speed output gear62, a 3rd speed output gear 64, a 5th speed output gear 66, a reverseoutput gear 68, a 2nd speed output gear 70 and a 4th speed output gear72. Thus, output gears 62–72 rotate around countershaft 46. Like inputgears 48–58, the number of output gears provided on countershaft 46 isnot limited to the number shown in FIG. 2.

Referring still to FIG. 2, 1st speed output gear 62, 3rd speed outputgear 64 and 5th speed output gear 66 are meshed with 1st speed inputgear 58, 3rd speed input gear 56 and 5th speed input gear 54,respectively. Similarly, reverse output gear 68, 2nd speed output gear70, and 4th speed output gear 72 are meshed with reverse input gear 52(through idler 94), 2nd speed input gear 48, and 4th speed input gear50, respectively. In another embodiment, transmission 24 may include asecond countershaft (not shown) that includes one or more of the outputgears rotatably disposed on first countershaft 44.

To countershaft 44 there is also integrally connected a final drivepinion gear 73 that rotates together with countershaft 44. Final drivepinion 73 is arranged perpendicular to an axis of a rotational outputmember 74, such as a final drive ring gear, and is meshed with outputmember 74. In the embodiment shown in FIG. 1, a transmission outputrotation from drive pinion 73 to output member 74 is distributed towheels 76 through a drive shaft 78 and a differential 80.

Referring again to FIG. 2, transmission 24 also includes axiallymoveable clutches 82, 84, 86 and 88, such as synchronized single ordouble acting dog-type clutches, which are splined to countershaft 44for rotation therewith. Clutch 82 is moveable by a conventional shiftfork (not shown) in an axial direction toward main clutch assembly 28 tofix countershaft 44 for rotation with 1st speed output gear 62.Similarly, clutch 84 may be moved in opposite axial directions torotationally fix output gear 64 or output gear 66 to countershaft 44.Clutch 86 may be selectively moved in opposite axial directions torotationally fix output gear 68 or output gear 70 to countershaft 44.Clutch 88 may be moved in an axial direction toward main clutch assembly28 to fix countershaft 44 for rotation with output gear 72. In anotherembodiment of the invention, clutches 82, 84, 86 and 88 may also beprovided on first and second input shafts 40, 42 to engage and disengagegears rotatably supported on input shafts 40, 42 in a mannersubstantially similar to the manner in which the gears are engaged oncountershaft 44.

In an embodiment of the invention, transmission 24 also includes axiallymoveable input shaft clutches 90 and 92, such as synchronized singleacting dog-type clutches, which are splined to first input shaft 40 forrotation therewith. In the illustrated embodiment, clutch 90 may bemoved in an axial direction toward main clutch assembly 28 to fix firstinput shaft 40 for rotation with second input shaft 42. Similarly,clutch 92 may be moved in an axial direction away from main clutchassembly 28 to fix first input shaft 40 for rotation with output member74.

As described above, ECU 30 delivers commands to the components ofpowertrain system 20 based on the receipt and evaluation of variousinput signals. These commands may include gear ratio interchangecommands to a shift control device that indirectly moves clutches 82,84, 86, 88, 90 and 92 to establish the gear ratios between first andsecond input shafts 40, 42 and countershaft 44. The shift control devicemay be a conventional device, such as, for example, an X-Yelectromechanical shift actuator system 100 (FIG. 1), or any othersuitable device that controls the axial position of each of clutches 82,84, 86, 88, 90 and 92 through a rail-type shift control mechanism 102(FIG. 1). Alternatively, clutches 82, 84, 86, 88, 90 and 92 may behydraulically and/or electromechanically operated without the use of arail-type shift control mechanism 102.

Operation of hybrid powertrain system 20 will now be described withreference to FIG. 2. In a first mode of operation employed duringvehicle launch and acceleration, first and second main clutches C1 andC2 are initially disengaged and clutch 82 is moved leftward from theneutral position shown in FIG. 2, so that 1st speed output gear 62 isfixed to countershaft 44 by clutch 82. Upon this movement, power fromfirst prime mover 22 may be transmitted to countershaft 44 by engagingsecond main clutch C2. The power applied to second input shaft 42 istransmitted through 1st speed input gear 58 to countershaft 44 through1st speed output gear 62, and then to final drive pinion 73 so that afirst speed ratio is established in transmission 24.

As the vehicle accelerates and the second speed ratio is desired, clutch86 is moved rightward from the neutral position shown in FIG. 2, so that2nd speed output gear 70 is fixed to countershaft 44 by clutch 86. Theengagement of clutch 86 occurs while first main clutch C1 is disengagedand no power is being transmitted from first prime mover 22 to firstinput shaft 40. Once clutch 86 is engaged, the currently engaged secondmain clutch C2 is disengaged while simultaneously or nearlysimultaneously engaging first main clutch C1. The resulting powerapplied to first input shaft 40 is transmitted through 2nd speed inputgear 48 to countershaft 44 through 2nd speed output gear 70, and then tofinal drive pinion 73 so that a second speed ratio is established intransmission 24. This process is repeated in the same manner forup-shifting through the remaining gear ratios, and in a reverse mannerfor down-shifting from one gear ratio to another.

To achieve the reverse gear in transmission 24, first and second mainclutches C1 and C2 are disengaged and clutch 86 is moved leftward fromthe neutral position shown in FIG. 2, so that reverse output gear 68 isfixed to countershaft 44 by clutch 86. The power applied to first inputshaft 40 is transmitted from reverse input gear 52 to countershaft 44through an idler gear 94 and reverse output gear 68, and then to finaldrive pinion 73.

Under a normal operating state, wherein transmission 24 assumes acertain speed gearing, both first and second main clutches C1 and C2 maybe kept in their engaged conditions while one of clutches 82, 84, 86,and 88 is kept at a given power transmitting position. For example, whentransmission 24 assumes the 5th speed ratio, both first and second mainclutches C1 and C2 may be engaged while clutch 84 is engaged with 5thspeed output gear 66 and clutches 82, 86 and 88 are in their neutralposition shown in FIG. 2. Although first and second main clutches areengaged, no power is transmitted through the unselected output gears 62,64, 68, 70 and 72 because the output gears are free to rotate oncountershaft 44 when not engaged by a corresponding clutch 82, 86 or 88.

Using main clutch 28, a vehicle employing hybrid powertrain system 20may be launched in a traditional manner under the power of first primemover 22 or a combination of first and second prime movers 22, 26.Alternatively, a vehicle employing powertrain system 20 may be launchedsolely under the power of second prime mover 26. In this manner, firstand second master clutches C1 and C2 are disengaged and second primemover 26 is operated to drive rotation of second input shaft 42.

In the embodiment shown in FIG. 2, gears 58 and 62 establish a “low”gear ratio between second input shaft 42 and countershaft 44 when clutch82 fixes gear 62 for rotation with countershaft 44. Because a vehicleemploying powertrain system 20 may be launched from rest solely underthe power of second prime mover 26, this “low” gear ratio provides thehighest torque output for a given torque input from second prime mover26, which will permit launching and initial acceleration of the vehicle.This ratio also provides the highest rotational speed for second inputshaft 42, which, when back-driven from the vehicle wheels, can be usedto quickly recharge energy storage device 31 during regenerative brakingof the vehicle as discussed in greater detail below. Gears 54 and 66establish a “high” gear ratio between second input shaft 42 andcountershaft 44 when clutch 84 fixes gear 66 for rotation withcountershaft 44.

When first prime mover 22 functions as an engine, the engine may bestarted prior to launching the vehicle using second prime mover 26 asthe “starter”. In an embodiment, the engine may be started by engagingclutch C2 to fix second input shaft 42 for rotation with flywheel 46,and then operating second prime mover 26 to apply power to second inputshaft 42 to drive rotation of flywheel 46. Alternatively, the engine canbe started after the vehicle is launched and traveled some distancesolely under the power of second prime mover 26. For example, withclutches C1 and C2 initially disengaged and second prime mover 26driving rotation of countershaft 44 through gears 58 and 62, input shaftclutch 90 can be engaged to fix first input shaft 40 for rotation withsecond input shaft 42. Then, with second prime mover 26 driving rotationof both first and second input shafts 40, 42, first main clutch C1 maybe engaged to drive rotation of flywheel 46 and start the engine.Alternatively, second main clutch C2 may be engaged to drive rotation offlywheel 46 without engaging input shaft clutch 90.

Once launched, the vehicle can be driven forward under the power offirst prime mover 22, second prime mover 26 or a combination of both.For example, when a combination of power from first and second primemovers 22, 26 is desired to drive countershaft 44 through one of gears62, 64 or 66, clutch C2 is engaged and power is applied directly toinput shaft 42 by both of first and second prime movers 22, 26.Alternatively, clutch C1 may be engaged and power applied indirectly toinput shaft 42 through clutch 90. In another example, when a combinationof power from first and second prime movers 22, 26 is desired to drivecountershaft 44 through one of gears 68, 70 and 72, either one of firstand second main clutches C1 and C2 is disengaged, input shaft clutch 90is engaged and power is applied directly to input shaft 40 by firstprime mover 22 (or indirectly through second input shaft 42) andindirectly by second prime mover 26 through second input shaft 42. Instill another example, clutch C1 may be engaged, clutch C2 may bedisengaged and power may be applied by second prime mover 26 throughsecond input shaft 42 and by first prime mover 22 through first inputshaft 40. The power applied to first input shaft 40 is then transmittedto countershaft 44 by operating clutch 86 or 88. Similarly, the powerapplied to second input shaft 42 is transmitted to countershaft 44 byoperating clutch 82 or 84.

As will be appreciated, first input shaft clutch 90 allows the powersupplied to second input shaft 42 by second prime mover 26 to beextended to first input shaft 40. Input shaft clutch 90 may also beengaged to provide compound gear reduction using one gear ratio fromfirst input shaft 40 and one gear ratio from second input shaft 42.Similarly, second input shaft clutch 92 allows the power supplied tofirst and second input shafts 40, 42 by first prime mover 22 and/orsecond prime mover 26 to be extended to rotational output member 74.Accordingly, second prime mover 26 may be operated either alone or incombination with first prime mover 22 to provide power to countershaft44 through one of gears 68, 70 and 72 or directly to output member 74.

As noted above, if reverse operation of the vehicle is required, ratiogear 68 is fixed for rotation with countershaft 44 by clutch 86 andfirst and/or second prime movers 22, 26 are operated to drive rotationof countershaft 44 through gears 52, 68 and 94. Alternatively, secondprime mover 26 may be operated alone to provide power for reverseoperation. In an embodiment, idler gear 94 may be removed to allow gears52 and 68 to mesh, and second prime mover 26 rotates second input shaft42 in a direction opposite its normal forward rotating direction.

Second prime mover 26 may also be used to provide the vehicle with an“anti-rollback” feature, i.e., application of torque to hold the vehicleat rest in stopped traffic or on a grade without the use of main clutchassembly 28. In an embodiment, both main clutches C1 and C2 aredisengaged, clutch 82 is engaged and second prime mover 26 is operatedto apply torque directly to second input shaft 42 to prevent rotation ofcountershaft 44. Depending on the weight of the vehicle and the grade tobe held, full torque slip of second prime mover 26 functioning as anelectric motor is typically less than approximately 1–2% of full motorspeed. Using an electric motor to provide “anti-rollback” torque is moreefficient than using first prime mover 22 functioning as an engine,which would require at least approximately 25% full torque slip throughmain clutch assembly 28 to hold a grade under similar operatingconditions.

During vehicle braking, second prime mover 26 may be selectively drivenby countershaft 44, through second input shaft 42, as an electricgenerator or a hydraulic pump to recharge energy storage device 31.Known as “regenerative braking,” this braking complements conventionalfriction braking to reduce the speed of the vehicle. During regenerativebraking, ECU 30 selectively controls operation of first prime mover 22,second prime mover 26 and transmission 24 for appropriate energyrecapture. For example, during vehicle braking, clutch 84 may be movedaxially to fix either ratio gear 64 or 66 for rotation with countershaft44. Rotation of countershaft 44 is then used to drive second input shaft42 and second prime mover 26. When operating as an electric generator,second prime mover 26 recharges a battery or bank of batteries. Whenoperating as a hydraulic pump, second prime mover 26 recharges ahydraulic accumulator. To eliminate drag and increase the regenerativeefficiency of regenerative braking, first prime mover 22 may bedisengaged from countershaft 44 by disengaging main clutches C1 and C2.However, to maintain vehicle stability during a downhill descent, ECU 30may be programmed to allow one of first and second main clutches C1 andC2 to remain engaged or partially engaged.

Another feature of the present invention is that first prime mover 22may be used to drive second prime mover 26 as an electric generator orhydraulic pump to recharge energy storage device 31. While the vehicleis at rest, main clutch C2 may be engaged allowing first prime mover 22to drive rotation of second input shaft 42 and the input portion ofsecond prime mover 26. Alternatively, input shaft clutch 90 may beselectively actuated to fix first input shaft 40 for rotation withsecond input shaft 42, as described above. With main clutch C2disengaged, main clutch C1 is then engaged to drive rotation of firstinput shaft 40, second input shaft 42 and the input portion of secondprime mover 26. Due to the properties of a four quadrant motor drive,energy storage device 31 functioning as a battery, bank of batteries ora capacitor may also be recharged while the vehicle is at cruise andsecond input shaft 42 is rotating. When second prime mover 26 functionsas an electric generator, first prime mover 22 may be used toselectively drive second prime mover 26 to supply electric power foron-board or off-board electrical equipment via the existing driveinverter. Similarly, when second prime mover 26 functions as a hydraulicpump, first prime mover 22 may be used to selectively drive second primemover 26 to provide fluid power for on-board or off-board hydraulicequipment.

From the above description it should now be apparent that hybridpowertrain system 20 offers a number of efficiency enhancing features.Among other features, the twin clutch transmission provides an improvedtransition from one gear ratio to another. Another feature is thatsecond prime mover 26 may also be used to supplement the torque providedby first prime mover 22 during vehicle acceleration to improve the fueleconomy through downsizing of the engine relative to the size requiredfor engine launch and acceleration alone. Yet another feature is thatsecond prime mover 26 alone may be used to launch the vehicle, therebyreducing the extent to which main clutch assembly 28 is used to improveits operative life. Additionally, second prime mover 26 may be employedas a motor to drive the vehicle in reverse, thereby eliminating the needfor reverse idler gearing to reduce transmission complexity.

Another feature is that second prime mover 26 may be operated as a motorto start first prime mover 22 (when first prime mover 22 functions as anengine), thus reducing the mass and space needed for a conventionalstarter motor. Still another advantage over prior art powertrain systemsis the virtual elimination of the undesirable parasitic load on thepowertrain resulting from second prime mover 26 drag when the vehicle iscruising under the sustained power of first prime mover 22.

Additionally, when operating as an electric generator or hydraulic pump,second prime mover 26 may be selectively operated to recover electricalor hydraulic energy during vehicle braking, to enhance fuel economy.Another feature is that energy storage device 31 may be recharged whilethe vehicle is at rest or while the vehicle is moving, by selectivelyengaging clutches C1, C2 and 90 as required. Still another feature isthat second prime mover 26 may be operated as an electric generator orhydraulic pump to power on-board or off-board electric or hydraulicdevices, while the vehicle is either at rest or moving.

The present invention has been particularly shown and described withreference to the foregoing embodiments, which are merely illustrative ofthe best modes for carrying out the invention. It should be understoodby those skilled in the art that various alternatives to the embodimentsof the invention described herein may be employed in practicing theinvention without departing from the spirit and scope of the inventionas defined in the following claims. It is intended that the followingclaims define the scope of the invention and that the method andapparatus within the scope of these claims and their equivalents becovered thereby. This description of the invention should be understoodto include all novel and non-obvious combinations of elements describedherein, and claims may be presented in this or a later application toany novel and non-obvious combination of these elements. Moreover, theforegoing embodiments are illustrative, and no single feature or elementis essential to all possible combinations that may be claimed in this ora later application.

1. A powertrain system, comprising: a change-gear transmission having afirst input shaft and a second input shaft; a first prime mover; a twinclutch that includes a first main clutch positioned between the firstprime mover and the first input shaft and a second main clutchpositioned between the first prime mover and the second input shaft; asecond input shaft clutch positioned between the first input shaft andthe second input shaft to selectively fix rotation of the first andsecond input shafts; and a second prime mover operably connected to oneof the first and second input shafts.
 2. The powertrain system of claim1, wherein the transmission includes a rotational output member.
 3. Thepowertrain system of claim 2, further including a first input shaftclutch positioned between the first input shaft and the rotationaloutput member to selectively fix rotation of the first input shaft withthe rotational output member.
 4. The powertrain system of claim 1,wherein the first prime mover is an internal combustion engine and thesecond prime mover is one of an electric motor and a hydraulic motor. 5.The powertrain system of claim 1, wherein the first input shaft includesat least one first input gear and the second input shaft includes atleast one second input gear.
 6. The powertrain system of claim 5,wherein the first and second input gears are secured to the first andsecond input shafts, respectively, for rotation therewith.
 7. Thepowertrain system of claim 5, wherein the transmission includes acountershaft having at least two countershaft gears, and wherein each ofthe first and second input gears are meshed with a correspondingcountershaft gear.
 8. The powertrain system of claim 7, wherein thecountershaft gears are rotatably supported on the countershaft.
 9. Apowertrain system, comprising: a change-gear transmission having a firstinput shaft, a second input shaft and a rotational output member, thechange-gear transmission also including a first input shaft clutchpositioned between the first input shaft and the rotational outputmember to selectively fix rotation of the first input shaft with therotational output member and a second input shaft clutch positionedbetween the first input shaft and the second input shaft to selectivelyfix rotation of the first and second input shafts; a first prime moveroperably connected to one of the first and second input shafts; a twinclutch that includes a first main clutch positioned between the firstprime mover and the first input shaft and a second main clutchpositioned been the first prime mover and the second input shaft; and asecond prime mover operably connected to the other of the first andsecond input shafts.
 10. A transmission and clutch arrangement for adual prime mover powertrain system, comprising; a change-geartransmission having a first input shaft, a second input shaft and arotational output member, the charge-gear transmission also including afirst input shaft clutch positioned between the first input shaft andthe rotational output member to selectively fix rotation of the firstinput it with the rotational output member and a second input shaftclutch positioned between the first input shaft and the second inputshaft to selectively fix rotation of the first and second input shafts;a twin clutch that includes a first main clutch configured toselectively transfer power between a first prime mover and the firstinput shaft and a second main clutch configured to selectively transferpower between the first prime mover and the second input shaft; andwherein at least one of the first and second input shaft is configuredfor connection to a second prime mover.